1. Field of the Invention
This invention relates to chainsaws. More specifically, it relates to a tensioning device that eliminates downtime associated with tensioning of the chainsaw cutting element.
2. Brief Description of the Related Art
A chainsaw includes an elongate flat bar that is attached by two (2) bolts and two (2) nuts to the body of the saw. This pair of adjustment screws is known in the industry as the externally threaded studs that protrude from the chainsaw motor block. A cutting element in the form of a chain circumscribes the bar. The chainsaw is used in a locked down position, i.e., the elongate flat bar cannot move when the chain is rotating.
As the saw is used, the chain links wear and stretch over time due to thermal expansion. The operator has to stop the saw because such expansion loosens the cutting element relative to the fixed position elongate flat bar. If the chainsaw is operated after the cutting element has become loose, the operator is in danger of serious injury. A cutting element can become loose in as few as six (6) to eight (8) minutes. A job that requires hours of cutting is thus frequently interrupted as the operator stops the saw in order to tighten the chain.
The exact chain-tightening procedure may vary from saw to saw, but the operator typically has to loosen at least one cam or bolt and turn a screw that is normally on the front of the saw, thereby putting the operator's hands near a hot sharp link. After loosening the bolts or cam the operator has to set the correct tension of the elongate flat bar and cutting element and re-tighten the loosened elements, i.e., the elongate flat bar is loosened so that it can be displaced in a proximal-to-distal direction in order to re-tighten the chain. The proximal end of the chain wraps around a fixed position sprocket so the proximal-to-distal displacement of the elongate flat bar, followed by re-tightening of the elongate flat bar in its new position, provides the required re-tensioning so that saw operation can resume. The procedure is time-consuming for professional saw operators and even more time-consuming as well as problematic for most noncommercial operators.
There is a longstanding need in the art of chainsaws for a structure that would eliminate the problem of having to shut down a chainsaw every few minutes in order to adjust the tension of the cutting element/chain.
More particularly, there is a need for a structure that would automatically maintain the tension on the chain for the life of the chain so that no shut down time would be required until the chain is so worn it can no longer cut.
The needed structure would not only save time, it would prevent serious injuries that occur when an operator fails to tighten a cutting element in a timely manner.
However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how a chainsaw could be modified to eliminate the need for frequent adjustments of the elongate flat bar.